1. Field of the Invention
The present invention relates to an arrayed waveguide grating optical multiplexer/demultiplexer and a method for manufacturing and using the arrayed waveguide grating optical multiplexer/demultiplexer.
2. Discussion of the Background
In recent years, in the field of optical communications, research and development in wavelength division multiplexing (WDM) transmission systems as a method for increasing the transmission capacity drastically have been actively pursued and the practical application is now advancing. The wavelength division multiplexing transmission systems, for example, multiplex a plurality of lights each having a different wavelength from each other and transmit the multiplexed light. In such wavelength division multiplexing transmission systems, an optical multiplexer/demultiplexer is required to multiplex a plurality of lights each having a different wavelength from each other and to demultiplex the multiplexed light to a plurality of lights each having a different wavelength from each other.
As an example of the optical multiplexer/demultiplexer, an arrayed waveguide grating (AWG) optical multiplexer/demultiplexer is known. Referring to FIG. 7A, an arrayed waveguide grating optical multiplexer/demultiplexer includes a substrate 11 and an optical waveguide unit 10 formed on the substrate 11. The optical waveguide unit 10 has a waveguide such as shown for example in FIG. 7A.
The arrayed waveguide grating optical multiplexer/demultiplexer includes one or more optical input waveguides 12 arranged side by side, a first slab waveguide 13 connected to the output ends of the optical input waveguides 12, an arrayed waveguide 14 connected to the output end of the first slab waveguide 13, a second slab waveguide 15 connected to the output end of the arrayed waveguide 14, a plurality of optical output waveguides 16 connected to the output end of the second slab waveguide 15 arranged side by side. The arrayed waveguide 14 includes a plurality of channel waveguides (14a) arranged side by side.
Each of the aforementioned channel waveguides (14a), which propagates the light outputted from the first slab waveguide 13, is formed of a predetermined different length from each other.
The optical input waveguide 12 or the optical output waveguide 16 is, for example, provided corresponding to the number of the signal lights each having a different wavelength from each other, for example, demultiplexed by arrayed waveguide grating optical multiplexer/demultiplexer. The channel waveguides (14a) are generally provided so many as for example 100 waveguides. But, for the purpose of simple illustration, the number of the waveguides of each waveguide (12, 14a, 16) is schematically shown in FIG. 7A. In addition, the arrayed waveguide grating optical multiplexer/demultiplexer is formed substantially symmetrical with respect to the broken line (C) in the drawing.
FIG. 7B shows the enlarged schematic view within the frame (A) depicted by dotted line in FIG. 7A. As shown in this figure, in the conventional arrayed waveguide grating optical multiplexer/demultiplexer, the output ends of the optical input waveguides 12 of a curved shapes are directly connected to the input side of the first slab waveguide 13. In addition, the input ends of the optical output waveguides 16 of curved shapes are directly connected to the output side of the second slab waveguide 15 likewise.
According to one aspect of the present invention, an arrayed waveguide grating optical multiplexer/demultiplexer includes at least one first optical waveguide, a first slab waveguide, an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide, a second slab waveguide, and a plurality of second optical waveguides connected to the arrayed waveguide via the second slab waveguide. The arrayed waveguide includes a plurality of channel waveguides each of which has a different length. The optical multiplexer/demultiplexer is configured to multiplex a plurality of lights having different wavelengths with a designed wavelength spacing and to demultiplex a light into a plurality of lights having different wavelengths with the designed wavelength spacing. The designed wavelength spacing is determined such that a value which is obtained by multiplying the designed wavelength spacing by an integer which is at least two is substantially equal to an actual wavelength spacing of lights which are input to or output from the multiplexer/demultiplexer.
According to another aspect of the present invention, a method for manufacturing an arrayed waveguide grating optical multiplexer/demultiplexer includes providing at least one first optical waveguide, providing a first slab waveguide and providing an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide. The arrayed waveguide includes a plurality of channel waveguides each of which has a different length. The method further includes providing a second slab waveguide and providing a plurality of second optical waveguides connected to the arrayed waveguide via the second slab waveguide. The optical multiplexer/demultiplexer is constructed to multiplex a plurality of lights having different wavelengths with a designed wavelength spacing and to demultiplex a light into a plurality of lights having different wavelengths with the designed wavelength spacing. The designed wavelength spacing is determined such that a value which is obtained by multiplying the designed wavelength spacing by an integer which is at least two is substantially equal to an actual wavelength spacing of lights which are input to or output from the multiplexer/demultiplexer.
According to further aspect of the present invention, a method for using an arrayed waveguide grating optical multiplexer/demultiplexer includes providing the arrayed waveguide grating optical multiplexer/demultiplexer. The optical multiplexer/demultiplexer includes at least one first optical waveguide, a first slab waveguide, an arrayed waveguide connected to the at least one first optical waveguide via the first slab waveguide, a second slab waveguide, and a plurality of second optical waveguides connected to the arrayed waveguide via the second slab waveguide. The arrayed waveguide has a plurality of channel waveguides each of which has a different length. The optical multiplexer/demultiplexer is configured to multiplex a plurality of lights having different wavelengths with a designed wavelength spacing and to demultiplex a light into a plurality of lights having different wavelengths with the designed wavelength spacing. A light having different wavelengths with an actual wavelength spacing is inputted to the at least one first optical waveguide or are outputted from the plurality of second optical waveguides. The actual wavelength spacing is substantially equal to a value obtained by multiplying the designed wavelength spacing by an integer which is at least two.